The present invention generally relates to an automatic gain control (will also be referred to as an xe2x80x9cAGCxe2x80x9d hereinafter) for gain controlling an input signal whose signal level is varied in a signal reception system of a mobile communication apparatus in such a manner that the level of the input signal is made constant by a feedback loop. More specifically, the present invention is directed to an automatic gain control device and an automatic gain control method, capable of switching an operation of a circuit employed in a control system in response to a condition of an automatic gain control operation, and also is directed to a radio communication apparatus having such an automatic gain control operation.
Conventionally, in various sorts of signal processing apparatuses, for example, radio communication apparatus, strengths of electromagnetic wave reception electric fields are varied by wave attenuate ions in electromagnetic wave propagation paths, so that signal levels of reception signals to be processed are varied. As a result, automatic gain control (AGC) operations are carried out in order to reduce demodulation errors, while making the variation of this reception signal constant. For instance, in portable telephones operated in the CDMA system, PDCs (personal digital cellular) of the TDMA system, and PHSs (personal handy-phone system) in the TDMA/TDD system, a strength of a signal reception electric field is detected from a reception signal, a gain of a variable gain amplifier is automatically controlled in response to this detection signal so as to make a constant level of an output signal. As such an automatic gain control manner, an open-loop control system and a closed-loop control system are known in this field. In the open-loop control system, a gain of a variable amplifier provided at a post stage is controlled in response to a control signal. This control signal is generated by detecting a level variation of an input signal. In the closed-loop control system, a gain of a variable gain amplifier provided at a prestage is controlled in response to this control signal.
In radio communication apparatus for executing such an automatic gain control, reductions of power consumption are required. More specifically, in the case of portable telephones, since rechargeable batteries are employed as power sources thereof, reductions of power consumed in these portable telephones are strongly required in order to prolong, or extend operable time of these portable telephones. Japanese Patent Application No. Hei-9-324111 filed by the Applicant in 1997 describes the radio base station apparatus capable of achieving the low power consumption in the system requiring the AGC circuit.
In the conventional signal processing apparatuses, even under such a condition that an automatic gain control becomes stable, for instance, even under such a stable reception condition that a strength of a reception electric field becomes constant (namely, non-move state in the case of portable telephone), this automatic gain control operation is continuously carried out. This execution may constitute one of factors as to why power consumption is increased. As a result, there is a problem that the power consumption cannot be reduced in the apparatus which requires the automatic gain control operation, and thus, the requirement for the long time operation of this signal processing apparatus can be hardly satisfied.
The present invention has been made to solve the above-explained problem, and therefore, has an object to provide an automatic gain control device, an automatic gain control method, and a radio communication apparatus having the automatic gain control function, capable of reducing power consumption while executing an automatic gain control operation, and capable of being driven for a long time period.
An automatic gain control device according to first aspect of the present invention, is an automatic gain control device in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control device comprises: control signal generating means for generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; control signal holding means for holding the variable gain control signal; and operation control means for bringing at least a portion of circuits of the relevant automatic gain control system into a non-operative condition in such a case that a condition detecting level based upon the input signal is not changed for a predetermined time period, and for sending out the variable gain control signal held by the control signal holding means to the variable gain amplifying means under the non-operative condition.
An automatic gain control device, according to second aspect of the present invention, is an automatic gain control device in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control device comprises: control signal generating means for generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; control signal holding means for holding the variable gain control signal; condition detecting level holding means for holding a condition detecting level in response to the input signal; condition detecting level difference calculating means for calculating a difference between a preceding condition detecting level and a present condition detecting level, which are held by the condition detecting level holding means; and operation control means for bringing at least a portion of circuits of the relevant automatic gain control system into a non-operative condition in the case that the difference of the condition detecting level is equal to zero, and for sending out the variable gain control signal held by said control signal holding means to the variable gain amplifying means under the non-operative condition; and also for releasing the non-operative condition of the circuit of the automatic gain control system when the difference of the condition detecting level is not equal to zero.
Also, according to third aspect of the invention, the operation control means uses the level of the variable gain control signal as the condition detecting level based upon the input signal; and when the level of the variable gain control signal is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to fourth aspect, the automatic gain control device is further comprised of detecting means for detecting the output signal to obtain a detection-signal; and the operation control means uses the level of the detection signal as the condition detecting level based upon the input signal; and when the level of the detection signal is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to fifth aspect, the automatic gain control device is further comprised of reception electric field strength detecting means for detecting a reception electric field strength of an input signal based upon the out signal; and the operation control means uses the reception electric field strength as the condition detecting level based upon the input signal; and when the reception electric field strength is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to sixth aspect, the automatic gain control device is further comprised of fading pitch detecting means for detecting a fading pitch of an input signal based upon the output signal; and the operation control means uses the fading pitch as the condition detecting level based upon the input signal; and when the fading pitch is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
A radio communication apparatus having an automatic gain control function, according to seventh aspect of the present invention, includes the structure of the automatic gain control device according to any one of first to sixth aspect of the invention is provided with a reception system of the radio communication apparatus; and the automatic gain control device executes an automatic gain control in such a manner that an output signal related to a reception signal received in the reception system is made constant.
An automatic gain control method, according to eighth aspect of the present invention, is an automatic gain control method in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control method comprises steps of: generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; detecting a change in a condition detecting level based upon the input signal; and bringing at least a portion of circuits of the relevant automatic gain control system into a nonoperative condition in such a case that the condition detecting level is not changed for a predetermined time period, and for sending out the held variable gain control signal to the variable gain amplifying means under the non-operative condition.
An automatic gain control method, according to ninth aspect of the present invention, is an automatic gain control method in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control method comprises steps of: generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; holding the variable gain control signal; holding a condition detecting level based upon the input signal, and calculating a difference between a preceding condition detecting level and a present condition detecting level; and bringing at least a portion of circuits of the relevant automatic gain control system into a non-operative condition in the case that the difference of the condition detecting level is equal to zero, and for sending out said held variable gain control signal to said variable gain amplifying means under the non-operative condition; and also for releasing the non-operative condition of the circuit of the automatic gain control system when the difference of the condition detecting level is not equal to zero.
Also, according to tenth aspect, as the condition detection level detected based upon the input signal, any one of the following level is employed, i.e., the level of the variable gain control signal; a level of a detection signal generated by detecting the output signal; a reception electric field strength of an input signal detected based upon the output signal; and a fading pitch of an input signal detected based on the output signal.
In the above-described automatic gain control device and method according to the present invention, while the input signal is variable-amplified by the variable gain amplifying means to obtain a predetermined output signal, the variable gain control signal is generated in response to the output signal level of the variable gain amplifying means, and this variable gain control signal is held, and then, the variable gain control signal is sent out to the variable gain amplifying means so as to perform the automatic gain control operation. Then, as the condition detection level detected based upon the input signal, while any one of the following levels is employed, i.e., the level of the variable gain control signal; a level of a detection signal generated by detecting the output signal; a reception electric field strength of an input signal detected based upon the output signal; and a fading pitch of an input signal detected based on the output signal, a change in this condition detecting level is detected. At is time, for example, while the condition detection level is held by the condition detection level holding means, the condition detection difference calculating means calculates a difference between the preceding condition detection level and the present condition detection level.
Furthermore, at least a portion of the circuits of the relevant automatic gain control system is brought into a non-operative condition in such a case that the condition detecting level based upon the input signal is not changed for a predetermined time period, and the held variable gain control signal is sent out to the variable gain amplifying means under this non-operation condition. Both a preselected time period (namely, stable condition continued time) during which the condition detecting level is not changed, and also a predetermined time (namely, operation stop continued time) during which the operation of the circuit of the automatic gain control system is stopped are measured by counting means such as a counter.
Alternatively, in the automatic gain control device, at least a portion of the circuits of the relevant automatic gain control system is brought into the non-operative condition in the case that the difference of the condition detecting level is equal to zero, and the held variable gain control signal to the variable gain amplifying means under the non-operative condition, and also the non-operative condition of the circuit of the automatic gain control system is released when the difference of the condition detecting level is not equal to zero.
Since such an operation control is carried out, the operation of the circuit provided in the automatic gain control system is stopped when the condition of the input signal becomes stable and the automatic gain control condition becomes stable. For example, in the case that the reception signal is handled as the input signal, both the reception electric field strength and the fading pitch is constant, and thus, the reception condition becomes stable, the circuit operation of the automatic gain control system is stopped. As a result, while the automatic gain control operation is carried out in high precision, the consumed power in the automatic gain control device can be reduced. Also, since this automatic gain control device and control method are applied to the radio communication apparatus, the power consumption of this radio communication apparatus may be reduced and also, this radio communication apparatus may be furthermore operated for a long time period. For instance, this automatic gain control function is especially effective as a power saving measure used in a portable telephone in which a rechargeable battery is employed as a power supply.